Polyester resin and method for producing polyester resin

ABSTRACT

A polyester resin containing: a diol constituent unit containing a unit a1 derived from spiroglycol represented by formula (1) and a unit a2 derived from ethylene glycol; and a dicarboxylic acid constituent unit containing a unit b derived from terephthalic acid and/or an ester thereof. A content of the unit a1 is from 5 to 60 mol % and a content of the unit a2 is from 30 to 95 mol %, based on a total amount of the unit a1 and the unit a2. A content of the unit b is from 80 to 100 mol % based on a total amount of the dicarboxylic acid constituent unit.

TECHNICAL FIELD

The present invention relates to a polyester resin and a method forproducing the polyester resin.

BACKGROUND ART

Polyethylene terephthalate (PET), which is a versatile polyester, iswell-known to be excellent in: mechanical properties such as tensilestrength, elongation, Young's modulus, and elastic recovery; physicalproperties such as thermal resistance and dimensional stability; andchemical properties such as chemical resistance and water resistance,and to require a low cost, and thus has significant industrial value.The polyethylene terephthalate has been widely used for, for example,fibers, tire cords, bottles, and films. However, in a field of sheetsrequiring transparency, PET crystallizes too fast and whitening tends tooccur due to crystallization at the time of secondary processing, andthus PET modified with cyclohexanedimethanol or the like has been used.Furthermore, in a field of bottles, to slow the crystallization speed ofPET, an expensive germanium compound has been used as a catalyst, andmodified PET produced by copolymerization using isophthalic acid orcyclohexanedimethanol as a modification component for the PET has beenused.

Meanwhile, because the modified PET described above and the like havepoor thermal resistance, use thereof tends to be limited in the fieldrequiring thermal resistance, such as fields of illumination boards,carports, and thermally resistant food containers. Taking this intoconsideration, a polyester resin produced by copolymerization with3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane(hereinafter, also referred to as “spiroglycol” or “SPG”) as a diolcomponent has been proposed. Specifically, for example, Patent Documents1 to 3 each propose a polyester resin containing an SPG-derivedconstituent unit or a production method thereof.

CITATION LIST Patent Document

Patent Document 1: JP 2008-260963 A

Patent Document 2: JP 2005-314643 A

Patent Document 3: JP 2003-212981 A

SUMMARY OF INVENTION Technical Problem

The present inventors have studied the polyester resins described inPatent Documents 1 to 3 and found that an intrinsic viscosity (IV) of apolyester resin tends to decrease when shearing is performed in atypical condition, and as a result, physical properties of a molded bodythereof tend to deteriorate.

The present invention has been completed in response to the above issuesof the conventional technologies, and an object of the present inventionis to provide a polyester resin with less reduction in intrinsicviscosity at the time of melt retention/melt extrusion, and a productionmethod thereof.

Solution to Problem

As a result of diligent research, the present inventors have found thatthe above issues can be solved by, in particular, adjusting physicalproperties of a polyester resin using a reduction percentage ofintrinsic viscosities before and after a predetermined meltretention/melt extrusion operation as an index, and thus completed thepresent invention.

That is, the present invention includes the following aspects.

[1]

A polyester resin comprising:

-   -   a diol constituent unit comprising a unit a1 derived from        spiroglycol represented by formula (1) and a unit a2 derived        from ethylene glycol; and    -   a dicarboxylic acid constituent unit comprising a unit b derived        from terephthalic acid and/or an ester thereof,    -   wherein    -   a content of the unit a1 is from 5 to 60 mol % and a content of        the unit a2 is from 30 to 95 mol %, based on a total amount of        the unit a1 and the unit a2,    -   a content of the unit b is from 80 to 100 mol % based on an        amount of all the dicarboxylic acid constituent unit, and    -   the following conditions (1) to (3) are satisfied:    -   (1) an intrinsic viscosity V1 of the polyester resin is from        0.45 to 0.85 dL/g, the intrinsic viscosity V1 being measured at        25° C. by using a mixed solvent comprising phenol and        1,1,2,2-tetrachloroethane in a weight ratio of 6:4;    -   (2) when an operation of extruding the polyester resin at a        shear rate of 122 (1/s) is performed after the polyester resin        is kept at 240° C. for 5 minutes, a reduction percentage of        intrinsic viscosities before and after the operation, in terms        of (V1−V2)/V1, is 3% or less, where V2 refers to an intrinsic        viscosity measured based on the condition (1) after the        operation; and    -   (3) a glass transition temperature of the polyester resin        measured by a differential scanning calorimeter is 90° C. or        higher and a heat quantity of a crystallization exothermic peak        during temperature decrease is 5 J/g or less.

[2]

The polyester resin according to [1], wherein the content of the unit bis from 95 to 100 mol %.

[3]

The polyester resin according to [1] or [2], wherein the content of theunit a1 is from 15 to 60 mol %, and the content of the unit a2 is from40 to 85 mol %, based on the total amount of the unit a1 and the unita2.

[4]

A method for producing the polyester resin according to any one of [1]to [3], the method comprising:

-   -   subjecting the ethylene glycol and the terephthalic acid and/or        an ester thereof to an esterification reaction to thereby        produce a precursor ester; and    -   adding the spiroglycol to the precursor ester,    -   wherein, in the adding, stirring is performed under a condition        expressed by expressions (A) and (B) below by using a stirrer        equipped with a stirring blade:

0.7011×log (spiroglycol addition rate (kg/hr))+1.339+0.5≥stirring bladetip speed (m/s)≥0.7011×log (spiroglycol addition rate (kg/hr))+1.339−0.5  expression (A)

0.5≤stirring blade tip speed (m/s)   expression (B).

[5]

The method for producing the polyester resin according to [4], wherein atemperature of the precursor ester in the adding is 195° C. or lower.

[6]

The method for producing the polyester resin according to [4] or [5],wherein storage, transfer, and addition of the spiroglycol are performedin an inert gas atmosphere.

[7]

The method for producing the polyester resin according to any one of [4]to [6], wherein a moisture content of the spiroglycol is 0.1 mass % orless.

Advantageous Effects of Invention

According to the present invention, a polyester resin with lessreduction in intrinsic viscosity at the time of melt retention/meltextrusion, and a production method thereof can be provided.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments for carrying out the present invention(referred to simply as “the present embodiments” below) will bedescribed in detail. The following embodiments are examples forexplaining the present invention, and do not limit the contents of thepresent invention. The present invention can be modified as appropriatewithin the scope of the gist. Note that, “(from) . . . to . . . ” in thepresent description includes both of the numerical values as the upperlimit value and the lower limit value unless otherwise noted.

Polyester Resin

The polyester resin of the present embodiment contains: a diolconstituent unit containing a unit a1 derived from spiroglycolrepresented by formula (1) (hereinafter, also simply referred to as“spiroglycol” or “SPG”) and a unit a2 derived from ethylene glycol; anda dicarboxylic acid constituent unit containing a unit b derived fromterephthalic acid and/or an ester thereof. A content of the unit a1 isfrom 5 to 60 mol % and a content of the unit a2 is from 30 to 95 mol %,based on a total amount of the unit a1 and the unit a2. A content of theunit b is from 80 to 100 mol % based on a total amount of thedicarboxylic acid constituent unit. The polyester resin of the presentembodiment the following conditions (1) to (3):

-   -   (1) an intrinsic viscosity V1 of the polyester resin is from        0.45 to 0.85 dL/g, the intrinsic viscosity V1 being measured at        25° C. by using a mixed solvent containing phenol and        1,1,2,2-tetrachloroethane in a weight ratio of 6:4;    -   (2) when an operation of extruding the polyester resin at a        shear rate of 122 (1/s) is performed after the polyester resin        is kept at 240° C. for 5 minutes, a reduction percentage of        intrinsic viscosities before and after the operation, in terms        of (V1−V2)/V1, is 3% or less, where V2 refers to an intrinsic        viscosity measured based on the condition (1) after the        operation; and    -   (3) a glass transition temperature of the polyester resin        measured by a differential scanning calorimeter is 90° C. or        higher and a heat quantity of a crystallization exothermic peak        during temperature decrease is 5 J/g or less.

Because the polyester resin of the present embodiment is configured asdescribed above, reduction of the intrinsic viscosity at the time ofmelt retention/melt extrusion becomes small. In more detail, forexample, difficulty in controlling extrusion pressure of an extruder(Note: this tendency will be significant especially when one lot ischanged to another) can be prevented at the time of melting for molding.

Diol Constituent Unit

The polyester resin of the present embodiment contains, as a diolconstituent unit, a unit a1 derived from spiroglycol represented byformula (1) above and a unit a2 derived from ethylene glycol. A contentof the unit a1 is from 5 to 60 mol % and a content of the unit a2 isfrom 30 to 95 mol %, based on a total amount of the unit a1 and the unita2. By blending the unit a1 and the unit a2 as described above, thepolyester resin of the present embodiment tends to have excellentbalance of thermal resistance, transparency, moldability, and mechanicalperformance.

From a similar viewpoint, the content of the unit a1 is preferably from15 to 60 mol %, and more preferably from 20 to 45 mol %. Similarly, thecontent of the unit a2 is preferably from 40 to 85 mol %, and morepreferably from 50 to 80 mol %.

Furthermore, from a similar viewpoint, the total amount of the unit a1and the unit a2 can be 47 mol % or greater, and is preferably 57 mol %or greater, and more preferably 72 mol % or greater, based on the amountof all the diol constituent units. The total amount of the unit a1 andthe unit a2 can be 100 mol %.

The polyester resin of the present embodiment may contain a unit a3derived from a diol other than the spiroglycol and the ethylene glycolas a diol constituent unit. Specific examples of the unit a3 include,but not limited to, units derived from: aliphatic diols such astrimethylene glycol, 2-methylpropanediol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol,propylene glycol, and neopentyl glycol; polyether compounds such aspolyethylene glycol, polypropylene glycol, and polybutylene glycol; tri-or higher polyhydric alcohols such as glycerin, trimethylolpropane, andpentaerythritol; alicyclic diols such as 1,3-cyclohexanedimethanol,1,4-cyclohexanedimethanol, 1,2-decahydronaphthalene dimethanol,1,3-decahydronaphthalene dimethanol, 1,4-decahydronaphthalenedimethanol, 1,5-decahydronaphthalene dimethanol,1,6-decahydronaphthalene dimethanol, 2,7-decahydronaphthalenedimethanol, tetralin dimethanol, norbornane dimethanol, tricyclodecanedimethanol,5-methylol-5-ethyl-2-(1,1-dimethyl-2-hydroxyethyl)-1,3-dioxane, andpentacyclodecane dimethanol; alkylene oxide adducts of bisphenols suchas 4,4′-(1-methylethylidene)bisphenol, methylenebisphenol (bisphenol F),4,4′-cyclohexylidenebisphenol (bisphenol Z), and 4,4′-sulfonylbisphenol(bisphenol S); and alkylene oxide adducts of aromatic dihydroxycompounds such as hydroquinone, resorcin, 4,4′-dihydroxybiphenyl,4,4′-dihydroxydiphenyl ether, and 4,4′-dihydroxydiphenylbenzophenone.

The content of the unit a3 can be 53 mol % or less, and is preferably 43mol % or less, and more preferably 28 mol % or less, based on the amountof all the diol constituent units. The content of the unit a3 can be 0mol %.

Dicarboxylic Acid Constituent Unit

The polyester resin of the present embodiment contains a unit b derivedfrom terephthalic acid and/or an ester thereof as a dicarboxylic acidconstituent unit. The content of the unit b is from 80 to 100 mol %based on the total amount of the dicarboxylic acid constituent unit. Byblending the unit b as described above, the polyester resin of thepresent embodiment tends to have excellent balance of thermalresistance, transparency, moldability, and mechanical performance.

From a similar viewpoint, the content of the unit b is preferably from95 to 100 mol %.

The polyester resin of the present embodiment may contain a unit b′derived from a dicarboxylic acid and/or an ester thereof other than theterephthalic acid and the ester thereof as a dicarboxylic acidconstituent unit. Specific examples of the unit b′ include, but notlimited to, units derived from isophthalic acid, phthalic acid,2-methylterephthalic acid, naphthalenedicarboxylic acid,biphenyldicarboxylic acid, tetralindicarboxylic acid, succinic acid,glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid,sebacic acid, dodecanedicarboxylic acid, cyclohexanedicarboxylic acid,decalin dicarboxylic acid, norbornanedicarboxylic acid,tricyclodecanedicarboxylic acid, pentacyclododecanedicarboxylic acid,isophoronedicarboxylic acid,3,9-bis(2-carboxyethyl)2,4,8,10-tetraoxaspiro[5.5]undecane, trimelliticacid, trimesic acid, pyromellitic acid, tricarballylic acid, and estercompounds of these.

Physical Properties of Polyester Resin

The polyester resin of the present embodiment satisfies the followingcondition (1):

-   -   (1) an intrinsic viscosity V1 of the polyester resin is from        0.45 to 0.85 dL/g, the intrinsic viscosity V1 being measured at        25° C. by using a mixed solvent containing phenol and        1,1,2,2-tetrachloroethane in a weight ratio of 6:4.

The intrinsic viscosity V1 of less than 0.45 dL/g is not preferredbecause handling of the polyester resin becomes difficult. Specifically,since the viscosity in a molten state is too low and mechanicalproperties are low causing brittleness, for example, it becomesdifficult to take out the product from the production apparatus of thepolyester resin and to pelletize. On the other hand, the intrinsicviscosity V1 of greater than 0.85 dL/g is not preferred because the meltviscosity at the time of processing of the polyester resin becomesexcessively large, fluidity may deteriorate, and excessive heating maybe required to achieve fluidity.

From a similar viewpoint, the intrinsic viscosity V1 is preferably from0.47 to 0.79 dL/g, and more preferably from 0.51 to 0.74 dL/g.

Specifically, the intrinsic viscosity V1 can be measured by the methoddescribed in Examples below.

For example, the intrinsic viscosity V1 can be adjusted to the rangedescribed above by appropriately adjusting a copolymerization ratio ofstarting monomers of the polyester resin.

The polyester resin of the present embodiment satisfies the followingcondition (2):

-   -   (2) when an operation of extruding the polyester resin at a        shear rate of 122 (1/s) is performed after the polyester resin        is kept at 240° C. for 5 minutes, a reduction percentage of        intrinsic viscosities before and after the operation, in terms        of (V1−V2)/V1, is 3% or less, where V2 refers to an intrinsic        viscosity measured based on the condition (1) after the        operation.

When the reduction percentage of the intrinsic viscosities is greaterthan 3% and processing into a molded body is performed, performancesthat can be potentially exhibited by the polyester resin serving as araw material cannot be exhibited, and as a result, mechanical propertiesand the like of the molded body are impaired.

From a similar viewpoint, the reduction percentage of the intrinsicviscosities is preferably 2.5% or less, and more preferably 2% or less.The lower limit value of the reduction percentage of the intrinsicviscosities is not particularly limited and may be 0%.

Specifically, the reduction percentage of the intrinsic viscosities canbe measured by the method described in Examples below.

For example, the reduction percentage of the intrinsic viscosities canbe adjusted to the range described above by employing a preferredproduction method described below or by removing a thermally modifiedproduct of unreacted SPG that can be generated in the production processof the polyester resin.

The polyester resin of the present embodiment satisfies the followingcondition (3):

-   -   (3) a glass transition temperature of the polyester resin        measured by a differential scanning calorimeter is 90° C. or        higher and a heat quantity of a crystallization exothermic peak        during temperature decrease is 5 J/g or less.

When the glass transition temperature is in the range described above,practically effective thermal resistance is achieved. When the heatquantity of the crystallization exothermic peak during temperaturedecrease is in the range described above, excellent transparency,moldability, and secondary processing are achieved.

From a similar viewpoint, the glass transition temperature is preferably97° C. or higher, and more preferably 105° C. or higher. Furthermore,the heat quantity of the crystallization exothermic peak duringtemperature decrease is preferably 3 J/g or less, more preferably 1 J/gor less, and even more preferably 0.1 J/g or less.

Specifically, the glass transition temperature and the heat quantity ofthe crystallization exothermic peak during temperature decrease can bemeasured by the methods described in Examples below. For example, theglass transition temperature and the heat quantity of thecrystallization exothermic peak during temperature decrease can beadjusted to the ranges described above by appropriately adjusting acopolymerization ratio of starting monomers of the polyester resin.

Method for Producing Polyester Resin

The polyester resin of the present embodiment is not particularlylimited as long as the configuration described above is achieved. In thepresent embodiment, from a viewpoint of efficiently producing apolyester resin having a lower reduction percentage of the intrinsicviscosities, the following production method is preferably employed.That is, a preferred method for producing the polyester resin of thepresent embodiment (hereinafter, also referred to as “production methodof the present embodiment”) includes:

-   -   subjecting the ethylene glycol and the terephthalic acid and/or        an ester thereof to an esterification reaction to thereby        produce a precursor ester (“esterification reaction step”); and    -   adding the spiroglycol to the precursor ester (“adding step”),    -   wherein, in the adding, stirring is performed under a condition        expressed by expressions (A) and (B) by using a stirrer equipped        with a stirring blade:

0.7011×log (spiroglycol addition rate (kg/hr))+1.339+0.5≥stirring bladetip speed (m/s)≥0.7011×log (spiroglycol addition rate (kg/hr))+1.339−0.5  expression (A)

0.5≤stirring blade tip speed (m/s)   expression (B).

Because the production method of the present embodiment is configured asdescribed above, the polyester resin with less reduction in intrinsicviscosity at the time of melt retention/melt extrusion can beefficiently produced.

Esterification Reaction Step

In the esterification reaction step, a precursor ester is formed byreacting the ethylene glycol and the terephthalic acid and/or an esterthereof. In the present embodiment, the esterification reaction can beconducted similarly to esterification process in known methods forproducing a polyester resin, and known conditions and catalysts can beused. Specific examples include a production method in which adicarboxylic acid and a diol are directly subjected to an esterificationreaction, and a production method in which a dicarboxylic acid and adiol are added to a seed oligomer and subjected to an esterificationreaction.

Adding Step

In the adding step, at the time of adding the spiroglycol to theprecursor ester, stirring is performed under a condition expressed byexpressions (A) and (B) by using a stirrer equipped with a stirringblade:

0.7011×log (spiroglycol addition rate (kg/hr))+1.339+0.5≥stirring bladetip speed (m/s)≥0.7011×log (spiroglycol addition rate (kg/hr))+1.339−0.5  expression (A)

0.5≤stirring blade tip speed (m/s)   expression (B).

In a case where the stirring is performed in a condition expressed byexpressions (A) and (B), a polyester resin can be synthesizedefficiently while attachment of SPG to a reactor gas phase part isprevented. Furthermore, because attachment of the SPG to the reactor gasphase part is small, an amount of impurities derived from unreacted SPG(deposits of thermally modified unreacted SPG) mixed into the polyesterresin can be made small, and thus the reduction percentage of theintrinsic viscosities can be significantly reduced.

As the stirrer, various known stirring apparatuses can be used. Specificexamples include, but not limited to, a stirring apparatus equipped witha stirring blade having an anchor shape.

In the production method of the present embodiment, the temperature ofthe precursor ester in the adding is not particularly limited but ispreferably 195° C. or lower from a viewpoint of SPG decompositionsuppression.

In the production method of the present embodiment, the atmosphere inwhich storage, transfer, and addition of the spiroglycol are performedis not particularly limited; however, from a viewpoint of prevention ofcoloring of a resin and a dust explosion due to mixing of oxygen, theseare preferably performed in an inert gas atmosphere.

In the production method of the present embodiment, the moisture contentof the spiroglycol is not particularly limited; however, from aviewpoint of SPG decomposition suppression at the time of charging intoa reactor, the moisture content is preferably 0.1 mass % or less.

Specifically, the moisture content can be measured by the methoddescribed in Examples below.

For example, the moisture content can be adjusted to the range describedabove by purging with a nitrogen gas having a dew point at atmosphericpressure of −50° C. or lower.

EXAMPLES

Hereinafter, the present embodiments will be described in further detailwith reference to examples, but the present embodiments are not limitedto these examples.

Evaluation Methods

The evaluation methods of the polyester resin in the present examplesare as described below.

(1) Composition of Polyester Resin Copolymerization Ratio of SPG

The copolymerization ratio of the SPG is a ratio of a structural unitamount of SPG to a dicarboxylic acid constituent unit amount in thepolyester resin (SPG copolymerization ratio). The ratio of the diol unitto the dicarboxylic acid unit in the polyester resin was calculatedbased on 1H-NMR analysis. The measurement was performed by ECA500 500MHz, available from JEOL Ltd., as a measurement instrument. By using adeuterated chloroform as a solvent, the measurement was performed bydissolving 50 mg of the polyester resin in 2 g of a solvent.

(2) Glass Transition Temperature and Crystallization Exothermic PeakDuring Temperature Decrease

The glass transition temperature (Tg) of the polyester resin wasmeasured by charging approximately 10 mg of a sample in an unsealedaluminum container and by using a differential scanning calorimeter(model: DSC/TA-60A), available from Shimadzu Corporation, at atemperature increase rate of 20° C./min in a nitrogen gas (50 mL/min)stream. The temperature at which change occurred in a degree of ½ of thedifference between base lines before and after transition of DSC curvewas used as the glass transition temperature. After the measurement ofthe glass transition temperature, the crystallization exothermic peakduring temperature decrease was measured based on an area of anexothermic peak appeared when the sample was maintained at 280° C. for 1minute and then temperature was decreased at a temperature decrease rateof 10° C./min.

(3) Intrinsic Viscosity (IV)

A polyester resin was heated and dissolved in a mixed solvent ofphenol/1,1,2,2-tetrachloroethane (mass ratio=6:4) at 90° C., and thussolutions of 0.2, 0.4, and 0.6 g/dL were prepared. The samples were thencooled to 25° C., and thus samples for measurement were prepared. Themeasurement was performed at a temperature of 25° C. by using Y501Relative Viscometer, available from Viscotek, as an instrument.

(4) SPG Moisture Content (wt. %)

The measurement of the moisture content of the SPG was performed byquantifying the moisture content in a vaporization condition at 160° C.for 20 minutes by using a Karl Fischer moisture meter (model: CA-200),available from Mitsubishi Chemical Corporation, and a moisture vaporizer(model: VA-236S), and thus the moisture content was determined.

Example 1

In a 1 L reaction tank equipped with an anchor blade having a diameterof 100 mm, a packed tower distillation column, a cold trap, a heatingdevice, a nitrogen introduction tube, and a hopper for spiroglycol(3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane;SPG) addition, 275.7 g of terephthalic acid (TPA) and 128.8 g ofethylene glycol (EG) were charged and subjected to an esterificationreaction by an ordinary method, and thus a precursor ester was formed.To the formed precursor ester, 77.3 g of EG and 43 mg of germaniumdioxide were further added, and depolymerization was performed at 225°C. and a normal atmospheric pressure. While generated water wasdistilled off from the reaction product, the reaction was furtherperformed for 1.5 hours. Then, 34 mg of tetra-n-butyl titanate, 31 mg ofpotassium acetate, and 63 mg of triethyl phosphate were added to thereaction product at 225° C. and the normal atmospheric pressure.Subsequently, heat treatment was performed at 225° C. and 13.3 kPa for 1hour, and thus unreacted EG was distilled off from the reaction product.After the temperature was lowered to 190° C., the pressure was returnedto the normal atmospheric pressure with nitrogen, and 236.4 g of SPG wasadded in 10 batches for 1 hour with each batch having 23.64 g. At thetime of SPG addition, each time, after a predetermined amount of the SPGwas charged in a hopper for addition, purging was performed with anitrogen gas having a dew point at atmospheric pressure of −50° C. orlower until the oxygen concentration became 1%, and then addition to thereaction tank was performed. The stirring rate in the reaction tank atthe time of addition was 150 rpm, and the stirring blade tip speed was0.8 m/s. After the pressure was reduced to 13.3 kPa, the reaction wasperformed for 1 hour, then the reaction product was gradually heated,the pressure was reduced, and finally, the polycondensation reaction wasperformed at 280° C. in a high vacuum (300 Pa or less). During thistime, based on the melt viscosity at 280° C., the stirring rate wasdecreased, and the reaction was terminated when a predetermined stirringtorque was achieved at 25 rpm, and thus a polyester resin was produced.This operation was performed for three times without cleaning thereaction tank, and thus a polyester resin of Example 1 was produced.This polyester resin was used for the measurement of (3) above, and themeasured intrinsic viscosity V1 was 0.68. Separately, the producedpolyester resin was maintained at 240° C. for 5 minutes, and then anoperation of extruding the polyester resin at a shear rate of 122 (1/s)was performed. This polyester resin was also used for the measurement of(3) above, and the measured intrinsic viscosity V2 was 0.67. Thus, thereduction percentage of the intrinsic viscosities before and after theoperation was 1.5%.

Note that the stirring conditions of Example 1 satisfied both ofexpressions (A) and (B):

0.7011×log (spiroglycol addition rate (kg/hr))+1.339+0.5≥stirring bladetip speed (m/s)≥0.7011×log (spiroglycol addition rate (kg/hr))+1.339−0.5  expression (A)

0.5≤stirring blade tip speed (m/s)   expression (B).

Furthermore, the SPG used in Example 1 was in an inert gas atmosphere atthe time of addition as well as at the time of storage and transfer inthe reaction system, and when the moisture content of the SPG wasmeasured by the Karl Fischer method, the moisture content was 0.1 mass %or less.

Example 2

In a 1 L reaction tank equipped with an anchor blade having a diameterof 100 mm, a packed tower distillation column, a cold trap, a heatingdevice, a nitrogen introduction tube, and a hopper for SPG addition,275.7 g of TPA and 118.5 g of EG were charged and subjected to anesterification reaction by an ordinary method, and thus a precursorester was formed. To the formed precursor ester, 87.6 g of EG and 43 mgof germanium dioxide were further added, and depolymerization wasperformed at 225° C. and a normal atmospheric pressure. While generatedwater was distilled off from the reaction product, the reaction wasfurther performed for 1.5 hours. Then, 34 mg of tetra-n-butyl titanate,31 mg of potassium acetate, and 133 mg of triethyl phosphate were addedto the reaction product at 225° C. and the normal atmospheric pressure.Subsequently, heat treatment was performed at 225° C. and 13.3 kPa for 1hour, and thus unreacted EG was distilled off from the reaction product.After the temperature was lowered to 190° C., the pressure was returnedto the normal atmospheric pressure with nitrogen, and 161.6 g of SPG wasadded in 10 batches for 1 hour with each batch having 16.16 g. At thetime of SPG addition, each time, after a predetermined amount of the SPGwas charged in a hopper for addition, purging was performed with anitrogen gas having a dew point at atmospheric pressure of −50° C. orlower until the oxygen concentration became 1%, and then addition to thereaction tank was performed. The stirring rate in the reaction tank atthe time of addition was 150 rpm, and the stirring blade tip speed was0.8 m/s. After the pressure was reduced to 13.3 kPa, the reaction wasperformed for 1 hour, then the reaction product was gradually heated,the pressure was reduced, and finally, the polycondensation reaction wasperformed at 280° C. in a high vacuum (300 Pa or less). During thistime, based on the melt viscosity at 280° C., the stirring rate wasdecreased, and the reaction was terminated when a predetermined stirringtorque was achieved at 25 rpm, and thus a polyester resin was produced.This operation was performed for three times without cleaning thereaction tank, and thus a polyester resin of Example 2 was produced.When the intrinsic viscosities were measured for this polyester resin inthe same manner as in Example 1, the intrinsic viscosity V1 was 0.54,the intrinsic viscosity V2 was 0.53, and the reduction percentage of theintrinsic viscosities was 1.9%.

Note that the stirring conditions of Example 2 satisfied both ofexpressions (A) and (B) above.

Furthermore, the SPG used in Example 2 was in an inert gas atmosphere atthe time of addition as well as at the time of storage and transfer inthe reaction system, and when the moisture content of the SPG wasmeasured by the Karl Fischer method, the moisture content was 0.1 mass %or less.

Example 3

In a 50 L reaction tank equipped with a double helical blade having adiameter of 330 mm, a packed tower distillation column, a cold trap, aheating device, a nitrogen introduction tube, and an SPG addition inlet,13.79 kg of TPA and 6.44 kg of EG were charged and subjected to anesterification reaction by an ordinary method, and thus a precursorester was formed. To the formed precursor ester, 3.87 kg of EG and 2.15g of germanium dioxide were further added, and depolymerization wasperformed at 225° C. and a normal atmospheric pressure. While generatedwater was distilled off from the reaction product, the reaction wasfurther performed for 1.5 hours. Then, 1.70 g of tetra-n-butyl titanate,1.55 g of potassium acetate, and 7.580 g of triethyl phosphate wereadded to the reaction product at 225° C. and the normal atmosphericpressure. Subsequently, heat treatment was performed at 225° C. and 13.3kPa for 1 hour, and thus unreacted EG was distilled off from thereaction product. After the temperature was lowered to 190° C., thepressure was returned to the normal atmospheric pressure with nitrogen,and 11.82 kg of SPG was added in 10 batches for 1 hour with each batchhaving 1.182 kg. At the time of SPG addition, each time, after apredetermined amount of the SPG was charged in a hopper for addition,purging was performed with a nitrogen gas having a dew point atatmospheric pressure of −50° C. or lower until the oxygen concentrationbecame 1%, and then addition to the reaction tank was performed. Thestirring rate in the reaction tank at the time of addition was 110 rpm,and the stirring blade tip speed was 1.9 m/s. After the pressure wasreduced to 13.3 kPa, the reaction was performed for 1 hour, then thereaction product was gradually heated, the pressure was reduced, andfinally, the polycondensation reaction was performed at 280° C. in ahigh vacuum (300 Pa or less). During this time, based on the meltviscosity at 280° C., the stirring rate was decreased, and the reactionwas terminated when a predetermined stirring torque was achieved at 25rpm, and thus a polyester resin was produced. This operation wasperformed for twice without cleaning the reaction tank, and thus apolyester resin of Example 3 was produced. When the intrinsicviscosities were measured for this polyester resin in the same manner asin Example 1, the intrinsic viscosity V1 was 0.68, the intrinsicviscosity V2 was 0.67, and the reduction percentage of the intrinsicviscosities was 1.5%.

Note that the stirring conditions of Example 3 satisfied both ofexpressions (A) and (B) above.

Furthermore, the SPG used in Example 3 was in an inert gas atmosphere atthe time of addition as well as at the time of storage and transfer inthe reaction system, and when the moisture content of the SPG wasmeasured by the Karl Fischer method, the moisture content was 0.1 mass %or less.

Example 4

A polyester resin of Example 4 was produced in the same manner as inExample 3 except for changing the stirring rate in the reaction tank atthe time of the SPG addition to 140 rpm and changing the stirring bladetip speed to 2.4 m/s. When the intrinsic viscosities were measured forthis polyester resin in the same manner as in Example 1, the intrinsicviscosity V1 was 0.69, the intrinsic viscosity V2 was 0.69, and thereduction percentage of the intrinsic viscosities was 0%.

Note that the stirring conditions of Example 4 satisfied both ofexpressions (A) and (B) above.

Example 5

A polyester resin of Example 5 was produced in the same manner as inExample 3 except for adding 11.82 kg of the SPG in 15 batches for 1.5hours with each batch having 0.788 kg. When the intrinsic viscositieswere measured for this polyester resin in the same manner as in Example1, the intrinsic viscosity V1 was 0.68, the intrinsic viscosity V2 was0.67, and the reduction percentage of the intrinsic viscosities was1.5%.

Note that the stirring conditions of Example 5 satisfied both ofexpressions (A) and (B) above.

Comparative Example 1

Production of a polyester resin was performed in the same manner as inExample 1 except for adding the SPG at once (added 236.4 g in one batchfor 6 minutes); however, the SPG aggregated in a liquid surface of theprecursor ester solution and the SPG was not dissolved into thesolution, and thus the polyester resin could not be synthesized. Notethat the stirring conditions of Comparative Example 1 did not satisfyexpression (A) above.

Comparative Example 2

A polyester resin of Comparative Example 2 was produced in the samemanner as in Example 1 except for changing the rotation rate to 75 rpmand changing the stirring blade tip speed to 0.4 m/s. When the intrinsicviscosities were measured for this polyester resin in the same manner asin Example 1, the intrinsic viscosity V1 was 0.68, the intrinsicviscosity V2 was 0.65, and the reduction percentage of the intrinsicviscosities was 4.4%. Note that the stirring conditions of ComparativeExample 2 did not satisfy expression (B) above.

Comparative Example 3

A polyester resin of Comparative Example 3 was produced in the samemanner as in Example 2 except for changing the rotation rate to 75 rpmand changing the stirring blade tip speed to 0.4 m/s. When the intrinsicviscosities were measured for this polyester resin in the same manner asin Example 1, the intrinsic viscosity V1 was 0.54, the intrinsicviscosity V2 was 0.51, and the reduction percentage of the intrinsicviscosities was 5.6%. Note that the stirring conditions of ComparativeExample 3 did not satisfy expression (B) above.

Comparative Example 4

A polyester resin of Comparative Example 4 was produced in the samemanner as in Example 3 except for adding 11.82 kg of the SPG in 3batches for 15 minutes with each batch having 3.94 kg. When theintrinsic viscosities were measured for this polyester resin in the samemanner as in Example 1, the intrinsic viscosity V1 was 0.67, theintrinsic viscosity V2 was 0.64, and the reduction percentage of theintrinsic viscosities was 4.5%. Note that the stirring conditions ofComparative Example 4 did not satisfy both of expressions (A) and (B)above.

Comparative Example 5

A polyester resin of Comparative Example 5 was produced in the samemanner as in Example 3 except for changing the rotation rate to 70 rpmand changing the stirring blade tip speed to 1.2 m/s. When the intrinsicviscosities were measured for this polyester resin in the same manner asin Example 1, the intrinsic viscosity V1 was 0.68, the intrinsicviscosity V2 was 0.64, and the reduction percentage of the intrinsicviscosities was 5.9%. Note that the stirring conditions of ComparativeExample 5 did not satisfy both of expressions (A) and (B) above.

Comparative Example 6

A polyester resin of Comparative Example 6 was produced in the samemanner as in Example 1 except for using the SPG in which the SPGmoisture content determined by the Karl Fischer method was adjusted to0.5 mass %. When the intrinsic viscosities were measured for thispolyester resin in the same manner as in Example 1, the intrinsicviscosity V1 was 0.69, the intrinsic viscosity V2 was 0.66, and thereduction percentage of the intrinsic viscosities was 4.3%. Note thatthe stirring conditions of Comparative Example 6 satisfied both ofexpressions (A) and (B) above.

Comparative Example 7

A polyester resin of Comparative Example 7 was produced in the samemanner as in Example 1 except that, after heat treatment was performedat 225° C. at 13.3 kPa for 1 hour and thus unreacted EG was distilledoff from the reaction product, the pressure was returned to a normalatmospheric pressure with nitrogen without lowering the temperature to190° C. and the SPG was added at 225° C. When the intrinsic viscositieswere measured for this polyester resin in the same manner as in Example1, the intrinsic viscosity V1 was 0.68, the intrinsic viscosity V2 was0.65, and the reduction percentage of the intrinsic viscosities was4.4%. Note that the stirring conditions of Comparative Example 7satisfied both of expressions (A) and (B) above.

For the polyester resins of Examples 1 to 5 and Comparative Examples 2to 7, the results of the measurements (1) to (3) described above areshown in Table 1.

TABLE 1 Com- parative Exam- Exam- Exam- Exam- Exam- Exam- ple 1 ple 2ple 3 ple 4 ple 5 ple 1 Resultant resin physical properties Tg (° C.)109  98 109 109 109 — SPG in diol (mol %)  45.7  31.1  45.8  45.7  45.7— constituent unit PTA in 100 100 100 100 100 — dicarboxylic acidconstituent unit Crystallization (J/g)   0   0   0   0   0 — exothermicpeak during temperature decrease Limiting   0.68   0.54   0.68   0.69  0.68 — viscosity V1 Limiting   0.67   0.53   0.67   0.69   0.67 —viscosity V2 Reduction (%)   1.5   1.9   1.5   0   1.5 — percentage ofintrinsic viscosities Stirring conditions Rotation rate rpm 150 150 110140 110 150 Blade diameter [mm] 100 100 330 330 330 100 Stirring blade(m/s)   0.8  0.8   1.9   2.4   1.9   0.8 tip speed SPG addition (kg/hr) 0.2364   0.1616  11.82  11.82   7.880   2.364 rate expression (A) Upper  1.4   1.3   2.6   2.6   2.5   2.1 limit expression Lower   0.5   0.5  1.6   1.6   1.5   1.1 (A) or limit expression (B) Com- Com- Com- Com-Com- Com- parative parative parative parative parative parative Exam-Exam- Exam- Exam- Exam- Exam- ple 2 ple 3 ple 4 ple 5 ple 6 ¹⁾ ple 6 ²⁾Resultant resin physical properties Tg (° C.) 109 98 109 109 109 109 SPGin diol (mol %) 45.5 30.6 45.8 45.8 45.5 45.6 constituent unit PTA in100 100 100 100 100 100 dicarboxylic acid constituent unitCrystallization (J/g) 0 0 0 0 0 0 exothermic peak during temperaturedecrease Limiting 0.68 0.54 0.67 0.68 0.69 0.68 viscosity V1 Limiting0.65 0.51 0.64 0.64 0.66 0.65 viscosity V2 Reduction (%) 4.4 5.6 4.5 5.94.3 4.4 percentage of intrinsic viscosities Stirring conditions Rotationrate rpm 75 75 110 70 150 150 Blade diameter [mm] 100 100 330 330 100100 Stirring blade (m/s) 0.4 0.4 1.9 1.2 0.8 0.8 tip speed SPG addition(kg/hr) 0.2364 0.1616 47.28 11.82 0.2364 0.2364 rate expression (A)Upper 1.4 1.3 3.0 2.6 1.4 1.4 limit expression Lower 0.5 0.5 2.0 1.6 0.50.5 (A) or limit expression (B) ¹⁾ SPG containing 0.5 wt. % H₂O was used²⁾ SPG was added at liquid temperature of 225° C.

The present application claims priority to a Japanese Patent Application(JP 2020-188436) filed on Nov. 12, 2020, the content of which isincorporated herein by reference.

1-3. (canceled)
 4. A method for producing a polyester resin comprising:a diol constituent unit comprising a unit a1 derived from spiroglycolrepresented by formula (1) and a unit a2 derived from ethylene glycol;and a dicarboxylic acid constituent unit comprising a unit b derivedfrom terephthalic acid and/or an ester thereof, wherein a content of theunit a1 is from 5 to 60 mol % and a content of the unit a2 is from 30 to95 mol %, based on a total amount of the unit a1 and the unit a2, acontent of the unit b is from 80 to 100 mol % based on a total amount ofthe dicarboxylic acid constituent unit, and the following conditions (1)to (3) are satisfied: (1) an intrinsic viscosity V1 of the polyesterresin is from 0.45 to 0.85 dL/g, the intrinsic viscosity V1 beingmeasured at 25° C. by using a mixed solvent comprising phenol and1,1,2,2-tetrachloroethane in a weight ratio of 6:4; (2) when anoperation of extruding the polyester resin at a shear rate of 122 (1/s)is performed after the polyester resin is kept at 240° C. for 5 minutes,a reduction percentage of intrinsic viscosities before and after theoperation, in terms of (V1−V2)/V1, is 3% or less, where V2 refers to anintrinsic viscosity measured based on the condition (1) after theoperation; and (3) a glass transition temperature of the polyester resinmeasured by a differential scanning calorimeter is 90° C. or higher anda heat quantity of a crystallization exothermic peak during temperaturedecrease is 5 J/g or less,

the method comprising: subjecting the ethylene glycol and theterephthalic acid and/or an ester thereof to an esterification reactionto thereby produce a precursor ester; and adding the spiroglycol to theprecursor ester, wherein, in the adding, stirring is performed under acondition expressed by expressions (A) and (B) by using a stirrerequipped with a stirring blade:0.7011×log (spiroglycol addition rate (kg/hr))+1.339+0.5≥stirring bladetip speed (m/s)≥0.7011×log (spiroglycol addition rate (kg/hr))+1.339−0.5  expression (A)0.5≤stirring blade tip speed (m/s)   expression (B).
 5. The method forproducing the polyester resin according to claim 4, wherein atemperature of the precursor ester in the adding is 195° C. or lower. 6.The method for producing the polyester resin according to claim 4,wherein storage, transfer, and addition of the spiroglycol are performedin an inert gas atmosphere.
 7. The method for producing the polyesterresin according to claim 4, wherein a moisture content of thespiroglycol is 0.1 mass % or less.